Submitted on February 16, 2006
Accepted on September 11, 2006
INACTIVATION OF NEUREGULIN-1 BY NITRATION
David E Nethery1, Sudakshina Ghosh2, Serpil C. Erzurum2, and Jeffrey A Kern1*
1 Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University Hospitals of Cleveland, Case Western Reserve University, Cleveland, Ohio, United States
2 Departments of Pathobiology and Pulmonary, Allergy and Critical Care Medicine, Cleveland Clinic Foundation, Lerner Research Institute, Cleveland, Ohio, United States
* To whom correspondence should be addressed. E-mail: jeffrey.kern{at}uhhs.com.
Nitration is a post-translational modification that can compromise protein function. We hypothesized that nitration of growth factors secreted in the lung may alter their interaction with their respective receptors, and modulate the normal growth and differentiation program induced by ligand/receptor interaction. We tested this hypothesis in vitro by nitration of neuregulin-1's (NRG-1) EGF-like domain and studying the effect on NRG-1's activity. Nitration of NRG-1's (nNRG-1) EGF-like domain resulted in an inability to activate its receptor, the HER2/HER3 heterodimer, as defined by loss of HER2 tyrosine phosphorylation induced by nNRG-1 in MCF-7 cells. Receptor activation was not restored with increasing nNRG-1 concentration or exposure times. nNRG-1 did not compete with NRG-1 for HER2/HER3 binding in competition assays. In addition, nNRG-1 no longer induced proliferation of the MCF-7 cell line, as MCF-7 cells exposed to nNRG-1 and NRG-1 concurrently had the same proliferation rate as that induced by NRG-1 alone. Thus, nitration of NRG-1's EGF-like domain caused it to loose its ability to bind and activate its receptor with loss of ligand-induced proliferation. Post-translational nitration of growth factors in states where reactive nitrogen species are increased may be an important means of regulating growth factor/receptor effects in the lung.
